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Math Help - Easy kinematics problem

  1. #1
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    Easy kinematics problem

    Hi! I'm dealing with this problem that seems to be very easy, however the teacher says I'm wrong, and I don't know where's my mistake (She didn't tell me). So I hope you can tell me where did I go wrong Here's the problem:

    A falling sky diver travels 64m in 2 seconds. How much will he travel in 8 seconds? (Ignore the air resistance)

    My solution:

    I used the equation y=yo+vot+1/2gt^2
    with

    y=64m
    y0=0m
    g=9.8 m/s^2
    t=2s

    Then I solved it for vo, obtaining vo=22.2 m/s. And finally obtained:

    y=(22.2)(8)+1/2g(8)
    ^2=491.2 m

    I don't know what did I do wrong, and the teacher didn't even tell me what was the right answer
    . I hope you guys help me figure it out. Thanks!
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  2. #2
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    Re: Easy kinematics problem

    Quote Originally Posted by Cesc1 View Post
    Hi! I'm dealing with this problem that seems to be very easy, however the teacher says I'm wrong, and I don't know where's my mistake (She didn't tell me). So I hope you can tell me where did I go wrong Here's the problem:

    A falling sky diver travels 64m in 2 seconds. How much will he travel in 8 seconds? (Ignore the air resistance)

    My solution:

    I used the equation y=yo+vot+1/2gt^2
    with

    y=64m
    y0=0m
    g=9.8 m/s^2
    t=2s

    Then I solved it for vo, obtaining vo=22.2 m/s. And finally obtained:

    y=(22.2)(8)+1/2g(8)
    ^2=491.2 m

    I don't know what did I do wrong, and the teacher didn't even tell me what was the right answer
    . I hope you guys help me figure it out. Thanks!

    What I understand from the question is that the diver has traveled in 2 seconds 64m then for another 8 seconds how much will he travel..

    So we can find his velocity after 2 seconds and then use it to find the distance he traveled in 8s..

    What you did is that u found his velocity when he just started travelling the 64 m..
    After that you need to find the velocity that he was traveling with after 2 seconds and substitute that in the second equation-which you used to find the distance..
    Thanks from Cesc1
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  3. #3
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    Re: Easy kinematics problem

    Quote Originally Posted by puresoul View Post
    What I understand from the question is that the diver has traveled in 2 seconds 64m then for another 8 seconds how much will he travel..

    So we can find his velocity after 2 seconds and then use it to find the distance he traveled in 8s..

    What you did is that u found his velocity when he just started travelling the 64 m..
    After that you need to find the velocity that he was traveling with after 2 seconds and substitute that in the second equation-which you used to find the distance..
    That's exactly what I had to do. Thanks!
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